Authorities on Wednesday identified the third person killed in Monday's train derailment in Washington state, as crews worked to reopen a section of interstate where the crash occurred.

Benjamin Gran, 40, was killed after Train 501 of Amtrak's Cascades service from Seattle to Portland, Oregon, careened off a bridge in DuPont at around 7:33 a.m., the Pierce County Medical Examiner's Office said Wednesday.

Rail enthusiasts Jim Hamre, 61, and Zack Willhoite, 35, also died in the accident, which injured scores of others, according to the president of the Rail Passengers Association and the medical examiner's office.

The train was speeding at 80 mph in a 30-mph zone of track when it derailed, federal investigators have said. It was the inaugural ride of the new route which was promised as a faster service between Seattle and Portland.

Gran pleaded guilty to possession of child pornography in 2013, was sentenced to two years in federal prison and was under lifetime federal supervision, according to court records and an official with the United States Probation and Pretrial Services for the Western District of Washington.

Gran's mother, Linda Daniels, told NBC affiliate KING 5 of Seattle that Gran was "Amtrak's biggest fan." She told the station he had turned his life around after the conviction and sentence and she blamed the crime on his "severe autism."

"He made a mistake. He paid for it," she told the station. "He died in the best part of his life."

At least 36 people remained hospitalized Wednesday, hospital officials said. Seventeen were listed as being in serious condition. There were 83 people on the train, five crew members and a technician, Amtrak's president and CEO has said.

The engine from an Amtrak train crash is checked by workers before being transported away from the scene on Dec. 20 in DuPont, Washington. Elaine ThompsonAP

Southbound Interstate 5 remained closed Wednesday afternoon as crews were clearing wreckage from the crash.

"The debris from the collision is extensive" and crews continue to find more in the hillside near the crash site, Claudia Bingham Baker, a spokeswoman for the Washington State Department of Transportation, said at a news conference Wednesday afternoon.

"Pulling out that debris is a very difficult and time-consuming process," she said. Two southbound lanes of I-5 were opened Wednesday evening, and the whole interstate could be open in time for the Thursday morning commute, the department said.

The locomotive and train cars have been cleared from the site, officials said. The federal National Transportation Board is investigating the crash.